Heat-shock proteins produced by two human melanoma cell lines: Absence of correlation with thermosensitivity

Two human melanoma cell lines, extremely different in their thermal sensitivity, were pulse-labelled with (³⁵S)-methionine after 60 min of exposure at 42°C. For both cell lines, fractionation of the intrinsically labelled proteins by polyacrylamide gel electrophoresis (PAGE) showed increased labelling of a polypeptide band of Mr 72,000, along with a slight reduction of overall protein synthesis. By two-dimensional electrophoresis, the Mr 72,000 band resolved into multiple pattern components of the same size but differing in isoelectric points. The absence of qualitative and quantitative differences between the two melanoma cell lines indicates that the different thermal sensitivities are unrelated to their ability to express the heat-shock proteins.